1. Technical Field
The present invention relates to an image forming device and an image forming method using an exposure head adapted to image a light beam emitted from a light emitting element with an imaging optical system.
2. Related Art
As the exposure head of this kind, there is known a line head adapted to image light beams emitted from a plurality of light emitting elements as a plurality of spots. In the line head (the exposure head in the document) described in JP-A-2004-66758, for example, there are arranged a corresponding number of light emitting elements to one line in a direction corresponding to the main scanning direction, and the light beams emitted from the respective light emitting elements are imaged as spots by a gradient index lens. Then, by sequentially forming a latent image of every line on a surface of a latent image carrier moving in a sub-scanning direction, a two-dimensional latent image corresponding to a desired image can be formed.
Incidentally, in order for achieving latent image formation with higher resolution, it is possible to use a line head having light emitting element groups obtained by grouping a plurality of light emitting elements. Specifically, in this line head, there is formed a plurality of light emitting element group columns, each of which has a plurality of light emitting element groups disposed at positions different from each other in a direction (a width direction) corresponding to a sub-scanning direction, disposed in a direction (a longitudinal direction) corresponding to a main-scanning direction. However, in the line head having a plurality of light emitting element groups disposed at positions different from each other in the width direction as described above, if a moving velocity of the surface of the latent image carrier varies, the position at which the latent image is formed is shifted in the sub-scanning direction, and in some cases, preferable latent image formation is not achievable.